This invention relates to a signalling and communication system for transmitting signals over active power lines for the purpose of regulating power demand.
The demand for power experienced by power companies varies throughout each twenty-four hour period. To assure an adequate power supply at all times generating capacity must be maintained or alternative supplies made available to handle the peak demand. Generally, this results in unused generating capacity during off-peak hours.
Methods under study to reduce the diurnal variations in electric power demand include time-of-day metering and remote control of specific customer appliances. The former system varies the cost of electricity over the course of a day to encourage customers to reduce consumption during peak demand and increase demand when excess supply is available. The latter method permits the power company to switch off various large power-consuming appliances such as electric water heaters or air conditioners. This will permit the power company to directly reduce its load during peak periods.
To be economically feasible a load control system in a power distribution network supplying numerous households and small businesses must permit remote control at the end user points from a central location such as a power house or substation. It would be prohibitively expensive to use a signal transmission system different from the power lines themselves. But if the power lines are employed to carry remote control signals, the system must be made unresponsive to ordinary noise encountered on such lines. Otherwise the system might inadvertently cut off or overcharged.